Based on J.J. Abrams depressing outlook on life, here’s my extremely short and simple theory on how LOST will ultimately end.
Ben and Sayid will orchestrate the execution of Widmore and everyone with knowledge of the island, including Penny. Ben and the Oceanic Six will return to the island. Every single Lostie, Other and Freighter will be dead. The six will live out their days working under Ben’s leadership on the island.